Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

085
FXUS63 KLOT 051149
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
Issued by National Weather Service Lincoln IL
549 AM CST Mon Jan 5 2026

.KEY MESSAGES...

- Above average temperatures in the 40s and 50s expected for the
  upcoming work week.

- A potential for light rain, drizzle, and fog this evening
  into Tuesday.

- A late week system will bring showers to the area followed by
  falling temperatures and snow chances for the weekend.

&&

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 333 AM CST Mon Jan 5 2026

Since late last evening, temperatures across most sites have
risen a degree or two amid some strong warm advection provided
by a southwesterly LLJ with around 40 kt being sampled at 925mb.
Early this morning, were sitting in the lower and middle 30s
around the area. Limited BL mixing has done away with most of
the gustiness, but sustained winds are staying up at around 10
to 15 mph bringing on wind chills in the 20s to start our
Monday. Winds will gradually be stepping down here through the
day as the LLJ departs to the east. Continued WAA, especially
through the morning hours, should grant much of the area a shot
at seeing 40s this afternoon, particularly near and south of
I-80. Upper 30s to near 40 are forecast farther north.

Meanwhile, last evenings clipper system that managed to stay
just out of reach to our north is now scooting across the Great
Lakes. In its wake, an expansive stratus deck is pushing south
through WI and fog can be found up into northern WI and
northeastern MN. This deck is expected to continue propagating
southward and spread atop our CWA after sunrise and cloud up our
morning. There is a signal for some patchy vis reductions north
of I-80 and west of the Fox Valley as ceilings build down later
this morning, but any noteworthy impacts to visibilities appear
unlikely. Forecast soundings would suggest that the low
ceilings should scatter some for the afternoon, but mostly
cloudy conditions are anticipated throughout the day.

A better signal for fog, as well as precip chances, exists this
evening and night as a clipper system moves across the area.
The storms warm front will cut directly across the CWA today and
fog is anticipated to develop near and north of the front
toward the end of the afternoon, which should roughly equate to
near and north of I-80. Precip associated with this system will
blossom this evening as the storm nears the Mississippi and
phases with another shortwave impulse passing to our north. Rain
showers are then favored across our north tonight into early
Tuesday while more drizzly activity is possible farther south as
the storm tracks across the local area. We should be looking at
all liquid precip while any wintry precip stays up into WI.
Most of the precip should eject to our east by the end of the
morning, but a few camps throw up some isolated light showers in
its wake into the evening. The denser fog coverage will also
ease up behind the departing system after the morning, but gray,
dreary conditions with some visibility restrictions look to
continue into the evening. Temperatures are again anticipated to
steady out, if not warm a few degrees, during the night with
the storm moving across and overnight temperatures are forecast
in the middle and upper 30s. Even warmer conditions are favored
for Tuesday with highs forecast in the 40s to near 50 degrees
across our south.

Doom

.LONG TERM...  (Tuesday Night through Sunday)
Issued at 333 AM CST Mon Jan 5 2026

A period of mild weather is expected through the mid week
period before conditions turn more active late in the week.
Accordingly, primarily dry conditions are forecast for Wednesday
into the first half of Thursday, with temperatures topping out
both days well into the 40s (around 50 south of I-80). Rain
chances are then expected to ramp-up across the area later in
the day Thursday into Thursday night in response to a
significant northward surge of Gulf moisture up the Mississippi
Valley in advance of the next Pacific impulse expected to eject
northeastward from the Baja of California out across the Mid-
Mississippi Valley. Over the past 24 hours, ensemble guidance
has come into better agreement with this first wave of
precipitation expected Thursday night into early Friday.
Accordingly, rain chances Thursday night into early Friday have
increased into 60-80% range. Also, with the prospects for
unseasonably high precipitable water values (1+, which is above
the 90 percentile for early January) there is even some concern
for some periods of moderate to heavy rainfall in the region.
Interestingly, recent ensemble runs from the EPS, GEFS and the
CMC have roughly 60-70% of the members with more than  of rain
across at least portions of our area, which is not bad
considering this is still 4 days away.

This initial lead Pacific impulse should shift off to our
northeast during the day on Friday. In its wake, we should not
experience much of a cold push, so we currently do not
anticipate any P-type issues into Friday. Instead, our main
forecast focus will be quickly turning to the next significant
southern stream trough expected to eject from the Desert
Southwest out across the Plains on Friday. Interestingly,
ensemble guidance continues to suggest that as this southern
stream trough shifts across the central CONUS late Friday into
Friday night, a northern stream impulse will be quickly digging
in across the Upper Midwest. At this time, it remains unclear at
this time how quickly these two waves may begin to phase with
one another, which in turn leads to some increased uncertainty
with the timing and type of additional precipitation late Friday
into Saturday. While this will ultimately need to be ironed out
in the coming days, what is more certain is that we will be
headed back into a colder (more typical) winter pattern for a
period this weekend.

Birk

&&

.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/...
Issued at 545 AM CST Mon Jan 5 2026

Key Messages:
MVFR CIGs possible for a period late this morning into the
afternoon.

IFR to LIFR CIGs likely (60%+ chance) after 08Z tonight through
Tuesday morning. Occasional drizzle and reduced VSBYs in Fog
also likely to accompany these low CIGs Tuesday morning.

All is currently quiet weather wise, and aside from the
possibility for a period of BKN MVFR CIGs for a period later
this morning into the afternoon, it appears this will continue
to be the case through the day. However, conditions are expected
to deteriorate later tonight as a quick moving area of low
pressure moves right across northern IL into early Tuesday
morning. As it does, increasing low-level moisture is expected
to foster the development of very low CIGs (IFR to LIFR), fog
and areas of drizzle Tuesday morning. The lowest conditions are
expected between 10Z through 16Z Tuesday, with only a gradual
improvement likely thereafter.

Winds will generally be light (less than 10kt) through the
period. Directions will be from the south-southwest through the
daylight hours today, before trending east-southeasterly with
the advance of the surface low tonight. A period of light (less
than 5 kt) and variable winds are then likely for a period under
the low around daybreak Tuesday morning, before winds trend
back westerly later Tuesday morning following the eastward
passage of the low.

Birk

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

Visit us at weather.gov/chicago